The double-deficit hypothesis and difficulties in learning to read a regular orthography.

Abstract

In 2 large longitudinal studies, we selected 3 subgroups of German-speaking children (phonological awareness deficit, naming-speed deficit, double deficit) at the beginning of school and assessed reading and spelling performance about 3 years later. Quite different from findings with English-speaking children, phonological awareness deficits did not affect phonological coding in word recognition but did affect orthographic spelling and foreign-word reading. Naming-speed deficits did affect reading fluency, orthographic spelling, and foreign-word reading. Apparently, in the context of a regular orthography and a synthetic phonics teaching approach, early phases of literacy acquisition (particularly the acquisition of phonological coding) are less affected by early phonological awareness deficits than are later phases that depend on the build up of orthographic memory. The double-deficit hypothesis was developed by Maryanne Wolf and Patricia Bowers as an extension of the dominant phonological-deficit explanation of developmental dyslexia (e.g., Bowers & Wolf, 1993; Wolf & Bowers, 1999). The phonologicaldeficit hypothesis postulates an early difficulty in acquiring phonological awareness, which interferes with the acquisition of grapheme-phoneme coding as a word recognition mechanism, which in turn results in reduced self-teaching of orthographic word representations (Share, 1995). The early problem with phonological awareness is seen as resulting from less sharp phoneme boundaries in speech perception (Fowler, 1991) or from less distinct phonological word representations (Elbro & Peterson, 1998). The double-deficit hypothesis acknowledges the phonological awareness deficit of dyslexic children but stresses a deficit in naming speed as a second and equally important cause of reading difficulties. The first demonstration that dyslexic children show impaired naming speed was provided by Denckla and Rudel (1976), whose Rapid Automatized Naming (RAN) Test became the standard assessment of naming speed. In the RAN test, a large array of repeatedly presented, well-known visual patterns (pictured objects, color patches, digits) has to be named as quickly as possible. Wolf, Bally, and Morris (1986) were the In:st to show that early differences in rapid naming are predictive of later reading difficulties. The double-deficit hypothesis is based on findings (reviewed by Wolf & Bowers, 1999) showing that, typically, there are only modest correlations between phonological awareness measures and RAN performance in groups of dyslexic children and that dyslexic children as a group exhibit both phonological awareness deficits and naming-speed deficits. From these findings,